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벽체일체형 강제순환 태양열온수기의 열성능 평가 (제1보 : 실증실험)
최태규(Taegyu Choi),홍희기(Hiki Hong) 대한설비공학회 2021 설비공학 논문집 Vol.33 No.8
With the declaration of carbon neutrality, Zero Energy Building (ZEB) has attracted interest. Since hot water load is not easy to save, supply through renewable energy is essential for ZEB implementation. In fact, solar energy is the most appropriate renewable energy that can be applied to high-rise buildings, with only the front wall receiving sunlight in each household. A building integrated solar water heater developed for that purpose was mainly of a natural circulation type. There were insufficient experiments and verification of overheating phenomenon about a forced circulation type. In this study, thermal performance of a building integrated forced circulation solar water heater was evaluated through one-year demonstration experiments such as acquired energy, efficiency, solar fraction, and solar utilization. Overheating experiments were also conducted without hot water load for 7 days in August, 2020 when solar radiation was high. During three months of winter when hot water load was high, heat collection efficiency was 43.9% and solar fraction was 57.0%, showing good thermal performance. During overheating tests in summer, the system temperature maintained below the water boiling point, thus ensuring safety.
IoT를 적용한 태양열시스템 유지관리 및 고장진단 방안
최태규(Taegyu Choi),이두영(Doo Young Lee),조성구(Sung-Goo Cho),홍희기(Hiki Hong) 대한설비공학회 2019 대한설비공학회 학술발표대회논문집 Vol.2019 No.-
Typical trouble patterns in solar thermal systems include heat transfer medium leakage and pump failure. The purpose of this study was to demonstrate the way Lee and Hong diagnose pump failure and heat transfer medium leakage. And introduce how IoT technology used in solar thermal system for maintenance and Failure diagnosis. Pump failure can be diagnosed by XOR with pump and flow switch signal. Heat transfer medium leakage can be diagnosed by self-manufactured fluid sensor. And fluid sensor was destroyed during experiments. It was chance to enhance stability of fluid sensor. With IoT technology, when failure happens solar controller can send pop up message to user’s smart device. And service center also get that message so they can handle it. Also, service center has server. So they can get all data from every solar thermal system. It helps service center to maintain its solar thermal system easily.
최성종(Sungjong Choi),김종성(Jongsung Kim),최태규(Taegyu Choi) 한국자동차공학회 2007 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-
Fretting damage can be observed in automobile and railway vehicle, fossil and nuclear power plant, aircraft etc. In the present study, railway axle material RSA1 used for evaluation of fretting fatigue life. Plain and fretting fatigue tests were carried out using rotary bending fatigue tester with proving ring and bridge type contact pad. Through these test, the following results are obtained: 1) it is found that the fretting fatigue limit of standard specimen decreased about 37% compared to the plain fatigue limit. 2) The early crack of Shinkansen type specimens initiated in contact area and final fractured below σamp=214 ㎫. 3) The early crack of all TGV type specimens initiated in rounded area and fractured. 4) Tire tracks and rubbed scars were observed in the oblique crack region and fatigue crack growth region of fracture surface. 5) The wear debris is observed on the contact surface, and oblique cracks at an earlier stage are initiated in contact area. These results can be used as useful data in a structural integrity evaluation of railway axle.
최성종(Sungjong Choi),최태규(Jongsung Kim),김종성(Taegyu Choi),권종완(Jongwan Kwon) 한국자동차공학회 2007 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-
Fretting damage can be observed in automobile and railway vehicle, fossil and nuclear power plant, aircraft etc. In the present study, railway axle material RSA 1 used for evaluation of fretting fatigue life. Plain and fretting fatigue tests were carried out using rotary bending fatigue tester with proving ring and bridge type contact pad. Through these test, the following results are obtained: 1) it is found that the fretting fatigue limit of standard specimen decreased about 37% compared to the plain fatigue limit. 2) The early crack of Shinkansen type specimens initiated in contact area and final fractured below σamp=289 MPa. 3) The early crack of all TGV type specimens initiated in rounded area and fractured. 4) The wear debris is observed on the contact surface, and oblique cracks at an earlier stage are initiated in contact area. These results can be used as useful data in a structural integrity evaluation of railway axle.
최성종(Sungjong Choi),배용탁(Yongtak Bae),김종성(Jongsung Kim),최태규(Taegyu Choi),김구년(Gunyeon Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Fretting is a kind of surface damage mechanism observed in mechanically jointed components and structures. The initial crack under fretting damage occurs at lower stress amplitude and lower cycles of cyclic loading than that under plain fatigue condition. This can be observed in automobile and railway vehicle, fossil and nuclear power plant, aircraft etc. In the present study, railway axle material RSA1 used for evaluation of fretting fatigue life. Plain and fretting fatigue tests were carried out using rotary bending fatigue tester with proving ring and bridge type contact pad. Through these experiments, it is found that the fretting fatigue limit decreased about 35% compared to the plain fatigue limit. In fretting fatigue, the wear debris is observed on the contact surface, and oblique cracks at an earlier stage are initiated in contact area. These results can be used as useful data in a structural integrity evaluation of railway axle.
Deep Learning-based Planetary Gear Fault Diagnosis using Frequency Domain Averaging
Jeongsan Kim(김정산),Iljeok Kim(김일적),Jungchan Kim(김정찬),Taegyu Choi(최태규),Seungchul Lee(이승철) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4
Planetary gearboxes are widely used throughout industries because it is easy to deal with large gear ratios. The conventional diagnostic method for the planetary gearboxes is to measure the signal with an accelerometer to check the corresponding frequencies to faults types. However, it is difficult to find fault frequencies of mixed planet gears, sun gears, and bearings, since multiple gears are operated simultaneously. In addition, much noise is inherent in the signal. While time synchronous averaging (TSA) is a widely used noise reduction technique that averages multiple vibration signals within one revolution of the gear, tach signal cannot be synchronized in case of planet gears. To overcome this issue, we apply frequency domain averaging, an averaging technique performed in the frequency domain, to planet gear signals to eliminate the unnecessary noise components. In addition, we designed a convolutional neural network (CNN) to distinguish 12 classes of defect signals which consist of planet gear faults, sun gear faults, bearing faults, and combinations of these generated under steady, acceleration, and deceleration conditions. The result shows over 98% accuracy for test data.